Geometry Proof - Parallel Lines

[Buzur]

Homework Statement

Given: AB \coprod CD ; \angleA \cong \angleC
Proof: AD \coprod BC

Homework Equations

Idk how to necessary finish it...

The Attempt at a Solution

Statement -------------- Proof
1. AB \coprod CD ; \angleA \cong \angleC ----------- 1. Given
2. I say \angleA is supp. \angleD and \angleB is supp. \angleC ----------- 2. If two parallel lines cut by a transversal, then same-side interior angles are supp.

3. AD \coprod BC ---------------- 3. Substitution Prop.

Homework Statement

 

[marty1]

I don't think you can prove that TRUE unless ∠ A = ∠ C exactly.

 

[Buzur]

they are equal.. it was in the given information!

 

[HallsofIvy]

Homework Statement

Given: AB \coprod CD ; \angleA \cong \angleC
Proof: AD \coprod BC


View attachment 51205

Homework Equations

Idk how to necessary finish it...

The Attempt at a Solution

Statement -------------- Proof
1. AB \coprod CD ; \angleA \cong \angleC ----------- 1. Given
2. I say \angleA is supp. \angleD and \angleB is supp. \angleC ----------- 2. If two parallel lines cut by a transversal, then same-side interior angles are supp.

3. AD \coprod BC ---------------- 3. Substitution Prop.

Homework Statement

What are you substuting into what? Are you saying you are substituting "AD"
for "AB" and "BC" for "CD" in the original statement? That's NOT what the "substitution prop." says! Nor can you simply substitute them into the theorem you stated about parallel lines and supplementary angles- you would need to use its converse which says that if a transversal cutting two lines forms supplementary angles then the lines are parallel.

 

[marty1]

they are equal.. it was in the given information!

check your symbol... ≅